In modern tape readers, information is stored on the tape in characters which are disposed in linearly spaced relationship along the tape. In the tape readers heretofore constructed, when the data receiving stations transitted a signal to the tape reader that it was no longer accepting data, the tape reader had to be able to stop very rapidly on the character that was over the read head when the signal was received. If the tape was not stopped very rapidly, the inertia of the tape driving mechanism would cause a number of characters, depending on the speed of the tape reader, to move by the read head. These characters were read when they moved by the read head, but the information could not be sent to the data receiving stations because those stations had already sent a signal that they would not accept data. Hence, these characters were lost.
The demand that the tape stop very rapidly and on character to prevent loss of data, subjected the tape to severe stresses which caused rapid tape deterioration. In addition, the tape reader had to be provided with complex and expensive braking mechanisms which added to their cost.
Furthermore, the requirement that tapes stop on character whenever the data receiving station sent a signal that it would no longer accept data, imposed limitations on the useful speed the tape reader could run.
The speed which data receiving stations can receive data varies widely because of their design and because of the equipment controlled by the data receiving station. Some stations can only receive data at a very slow rate, while others can receive data at a very high rate. Accordingly, it is desireable for the tape reader to have the capacity for high speed operation but to have sufficient controls so that it can operate at any speed which the data receiving stations require.
What is needed, therefore, and comprises an important object of this invention, is to provide a tape reader which can operate at various speeds and which can coast to a stop without losing any characters when the data receiving station fails to signal the tape reader that it wants data.
A further object of this invention is to provide a tape reader with a buffer positioned between the tape reader and the data receiving stations, which functions to store, in the proper sequence, characters on the tape which move by the tape head, thereby permitting the tape reader to slow the tape gradually to a stop and thus eliminate wear and tear on the tape when the data receiving station signals that it is no longer receiving data.